Earth-like Planets May Be Very Common

The topic of extra-solar planets that may harbor life has been a lively one lately. Earlier this year we wrote Ken Ham Says There’s No Extraterrestrial Life. But that was based on scripture and speculation. Then some astronomical evidence was found.

Nearly one in four stars like the sun could have Earth-size planets, according to a University of California, Berkeley, study of nearby solar-mass stars.

How’s that for a good start? Let’s read on:

UC Berkeley astronomers Andrew Howard and Geoffrey Marcy chose 166 [type] G and [type] K stars within 80 light years of Earth and observed them with the powerful Keck telescope for five years in order to determine the number, mass and orbital distance of any of the stars’ planets. The sun is the best known of the G stars, which are yellow, while K-type dwarfs are slightly smaller, orange-red stars.

They looked at 166 of those stars within only 80 light years of us? Astronomically speaking, that’s virtually right next door. We’ve seen estimates that 1 in 13 stars in our “neighborhood” (a “tiny” region of roughly 3 million stars) is type G, and 1 in 8 is type K. This galaxy is estimated to be about 100,000 light years in diameter, containing at least 200 billion stars, so the number of such stars in just this galaxy is enormous.

What did Howard and Marcy find? We continue:

The researchers found increasing numbers of smaller planets, down to the smallest size detectable today – planets called super-Earths, about three times the mass of Earth.

“Of about 100 typical sun-like stars, one or two have planets the size of Jupiter, roughly six have a planet the size of Neptune, and about 12 have super-Earths between three and 10 Earth masses,” said Howard, a research astronomer in UC Berkeley’s Department of Astronomy and at the Space Sciences Laboratory. “If we extrapolate down to Earth-size planets – between one-half and two times the mass of Earth – we predict that you’d find about 23 for every 100 stars.”

The creationists aren’t going to like this. We look forward to posting about their reactions. Here’s more from UC Berkeley:

“This is the first estimate based on actual measurements of the fraction of stars that have Earth-size planets,” said Marcy, UC Berkeley professor of astronomy. Previous studies have estimated the proportion of Jupiter and Saturn-size exoplanets, but never down to Neptunes and super-Earths, enabling an extrapolation to Earth-size planets.

Okay, it’s just an “extrapolation.” Nevertheless, things are looking good out there for the possibility of finding planets like our own. Moving along:

“What this means,” Howard added, “is that, as NASA develops new techniques over the next decade to find truly Earth-size planets, it won’t have to look too far.”

Extrapolating further, this means that life is likely to be everywhere! But there’s also this:

“Just where we see the most planets, models predict we would find no cacti at all,” Marcy said. “These results will transform astronomers’ views of how planets form.”

9 responses to “Earth-like Planets May Be Very Common”

Well, they didn’t actually find any Earth-like planets. What they did was look at what the stars are doing and calculate what sizes of planets in what orbits would be compatible with the observations, given our theories of planetary formation.

Earth-like pretty much refers only to the size of the planet. Mercury, Venus, and Mars are also “Earthlike”.

Not saying it was a waste of time. But we don’t need to fire up the colony ship just yet.

Incidentally did you read about the Hundred Year Starship? ( I know one of the guys who wrote the paper, we’re in the same building):

to attain it would require not only major international cooperation, but a return to the exploration spirit and risk-taking ethos of the great period of Earth exploration, from Columbus to Amundsen, but which has nowadays being replaced with a culture of safety and political correctness.

Gabriel Hanna, the biggest problem with the Hundred Year Starship program is that the people who go would be dependent on governmental funding of an endless series of additional ships to keep them supplied. I’d like to go, but I’d be reluctant to assume that the program wouldn’t get shut down by some future Congress that would prefer to spend the money on food stamps or something. If your life literally depends on politicians, you’re as good as dead.

I’d like to go, but I’d be reluctant to assume that the program wouldn’t get shut down by some future Congress that would prefer to spend the money on food stamps or something. If your life literally depends on politicians, you’re as good as dead.

Six words: The Moon is a Harsh Mistress.

No, you have a really good point, but I’d take the chance. The risk would concentrate the minds of the expedition wonderfully on remaining self-sufficient.

But the price of sending supplies from Earth to Mars isn’t that much more than sending them to the International Space Station. Nearly all of the energy expenditure is getting up to Earth orbit. Getting to Mars is a piece of cake, energywise, if time isn’t a factor.

Did you ever wonder how many sun-like stars are visible with the naked eye?

While the calculations suggest there are no shortage of them in our galaxy, it turns out they are very hard to see without optical aid. Why is that?

Because stars like our sun are puny when it comes to energy output (luminosity) when compared to really bright energetic stars that dominate our night sky. Basically, most of the sun like stars get obliterated from our view by the inverse square law. What more interesting to contemplate is that for any putative alien life form staring up into its night sky, the same is true of the Earth’s sun from their point of view — it is not bright enough to reach the minimum level of brightness for human eye visibility beyond a few dozen light years.

So back to the question: how many sun-like stars are there that are visible to the naked eye? I believe the answer is 3; one of which ( (Alpha Centauri) lies below the horizon for most Northern Hemisphere viewers. Of the ones that can be seen by those of us in the Northern latitudes, Eta Cassiopeiae is the most easily found. It’s the faint magnitude 3.5 star in Cassiopeia, just off of the line that forms a “W” when you connect the brightest stars in that constellation, and lies about just 20 light years away.

Even at that close a distance, it is so feeble and faint (as would our own sun seen from that distance) that it is probably not visible to the naked eye from big cities with significant ambient artificial lighting.